The cells of the immune system are indispensable to protect us from invading pathogens and provide long-lasting immunity to re-infection. Essentially all of the 15 principal investigators at Trudeau Institute are funded and dedicated to study the fundamental mechanisms governing acute and long-lasting immune cell responses to infection and explore their potential for vaccine development. In order to study the properties and functions of these cells it is required to isolate distinct populations based on their unique phenotype. However, many of these immune cells, such as memory T cell subsets, dendritic cell subsets or basophils, are very rare and can only be identified by a combination of numerous phenotypic markers. Moreover, the increasing use of transgenic animals carrying fluorescent marker proteins excludes the use of non-fluorescent isolation methods such as magnetic beads. For these reasons a high speed multi-parameter fluorescence activated cell sorter is indispensable to effectively sort infrequent immune cells based on a combinatorial array of fluorescence parameters. While all investigators at Trudeau Institute have been using a cell sorter for many years the existing instrument is almost a decade old and poses critical limitations with respect to speed, the number of usable fluorochromes as well as the service and parts support by the manufacturer which will expire by the end of 2010. The requested MoFlo XDP High Speed Cell Sorter will overcome all of these limitations and will allow us a) to sort at significantly higher speed, which is critical to sort rare populations and generate more user time due to shortened sorts, b) to sort based on more independent fluorescence parameters, which is critical for the identification of particular immune cell subsets, c) to increase the effective sorting available to all investigators due to a significantly shortened setup period, d) ensure continued service and parts support by the manufacturer, Beckman Coulter. Although the individual experiments and procedures used by the investigators will likely change over time, the open architecture of the requested sorter was designed by the manufacturer to facilitate future modifications as needed. This instrument will be exclusively operated and maintained by the dedicated full-time personnel of the Flow Cytometry Core Facility. Because the research efforts of essentially all investigators are critically dependent on a high speed cell sorter Trudeau Institute is fully committed to provide all the necessary support to house and maintain this instrument in the future. PUBLIC HEALTH RELEVANCE: The cells of the immune system are indispensable for protecting us from invading pathogens and provide long-lasting immunity to re-infection. Many of these cells are rare and can only be identified by a combination of numerous parameters. In order to study the properties and functions of these cells we need to be able to isolate distinct populations based on their unique features.